No extensive research into the effects of navigation systems on crash risk has been done; firm conclusion about effectiveness may therefore not be drawn (see the archived SWOV fact sheet Safety effects of navigation systems ). A survey among Dutch lease car drivers  showed that the group with a navigation system had 10% less crashes for the distance travelled and claimed 5% lower costs (per crash).
Theoretically, there are both advantages and disadvantages. Better navigation implies fewer detours and less traffic exposure. Searching is no longer necessary, which means more attention may be paid to traffic. Drivers know when they will arrive, which leads to less stress. But if destinations are set during driving, or if the screen is in an awkward position, distraction will in fact increase. If drivers are directed from safe motorways to less safe secondary roads, this will be detrimental. The same goes when the digital map is inaccurate or no longer accurate. The share of car drivers with a navigation system is high (also see the question How often do people use ITS/ADAS provisions in their vehicles?).